1. Field of the Invention
Methods and apparatuses consistent with the present invention relates to bit interleaving, and more particularly, bit interleaving which can satisfy a WiMedia Ultra-Wideband physical layer specification (UWB PHY spec).
2. Description of Related Art
Bit interleaving is performed so that a communication system can be robust against a burst error. Specifically, bit interleaving can acquire a frequency diversity effect in a frequency hopping method, such as a multi-band orthogonal frequency division multiplexing (MB-OFDM) scheme. In the MB-OFDM scheme, latency may be reduced by limiting bit interleaving to less than three OFDM symbols.
Here, bit interleaving of the MB-OFDM scheme includes two operations. A first operation corresponds to a symbol interleaving operation. A second operation corresponds to a tone interleaving operation.
Tone interleaving enables a frequency diversity effect to be acquired between tones in a single sub-band by scattering data in a single OFDM symbol.
As an example, when a number of coded bits per OFDM symbol is 100, symbol interleaving with respect to a bit stream containing three symbols may be represented as,
0, 1, 2, 3, 4, 5, . . . , 299
→0, 3, 6, 9, . . . , 297, 1, 4, 7, 10, . . . , 298, 2, 5, 8, 11, . . . , 299
Also, tone interleaving with respect to a result of the symbol interleaving may be represented as,
0, 3, 6, 9, . . . , 297, 1, 4, 7, 10, . . . , 298, 2, 5, 8, 11, . . . , 299
→0, 30, 60, 90, . . . , 270, 3, 33, 63, 93, . . . , 273, 6, 36, 66, 96, . . . , 276, . . . .
U.S. Patent Publication No. 20040178934 discloses in detail a symbol interleaver and a tone interleaver for performing symbol interleaving and tone interleaving respectively.
When performing only symbol interleaving and tone interleaving, interleaving may be easily performed by simply arranging input data two-dimensionally in a storage space and appropriately reading the arranged input data. However, WiMedia UWB PHY spec 1.0 performs interleaving by adding an “intra-symbol cyclic shift” function.
Specifically, WiMedia UWB PHY spec 1.0 performs symbol interleaving and tone interleaving, and also performs a cyclic shift. Thus, when simply reading a memory as in a conventional art, interleaving may not be generally performed.
Accordingly, a new type of bit interleaver and bit interleaving method which can perform bit interleaving including a cyclic shift without adding complex hardware is required.